Adjustable strut.



EDWARI) 0. KEilLTGE, (3F CINCINNATI, OHIO.

1333 USTABLE STRUT.

Specification of Letters Patent.

Application filed September 8, 1915. Serial No. 49,631.

To all whom it may concern:

Be it known that I, EDWARD 0. Karma, a citizen ofthe United States of America, and resident of Cincinnati, county of Hamilton, State of Ohio, have invented certain new and useful Improvements in Adjustable Struts, of which the following is a specifi cation. V

This invention relates to improvements in adjustable struts for supporting temporary form work for concrete construction and has for an object to produce an adjustable strut in which the relatively movable members may be positively adjusted to'prevent an initial giving or settling thereof when the load is placed on the strut.

A further object is to produce an adjustable strut in which the grip oi its clampswill increase in direct proportion to the load placed on the strut.

These and other objects are attained in the strut illustrated in the accompanying drawings and described in the following specification in which:

Figure 1 is a side elevation of a strut embodying my invention. Fig, 2 is a fragmental side elevation upon an enlarged scale of a strut embodying my invention, certain parts being shown in section. Fig. 3G 3 is a perspective view upon an enlarged scale of an automatic clamp embodying my invention.

Heretofore in struts oft-he adjustable type, clamping members have been our ployed which when set to lock the adjustable members of the strut in their adjusted positions for receiving a load, would never? theless permit the members oi he strut to give or settle to a certain extent before finally supporting the load without further relative movement of the membersv This settling is variable in amount an allowance has to be made therefor in setting up form work, by providing suitable means such as wedges for lifting the form work the amount the members of the strut have settled. In order to overcome this objection to struts heretofore employed I have devised the strut hereinafter described and illustrated in the accompanying drawings which consists of a central support member recent-ea Sept. is, rare.

4 adapted to rest upon the strutsupporting I surface, and side support members 5 and 6 located on opposite sides of the central support member and connected at their top ends by means of a block 7, with plates d-secured thereto intermediate the ends of the side members and embracing the remaining opposite sides of the central support member, the plates preventing displacement of the side support members from the central support member. The lower ends of the side support members. are free and are adajpted to be pressed against the opposite sides of the central support member to frictionally lock the side support members thereto.

In order to bring the free ends of the side support members into clamping frictional engagement with the central support member I have provided a clamping device 9. This clamping device consists of plates 10 located on each side of the central and side support members and connected at their ends by means of bolts 11 and 12. Bolt 11 forms a journal pin for an eccentric clamp 13 the surface of which engages a plate 14: secured to the end of the side support member 5. Member 5' is preferably somewhatlonger than support member 6 and the bolt 12 is of member 6. Thisbolt forms a journal pin for an automatic clamp 15 which engages both the side of. the central support memher 4. and the lower end face of the side support member 6. The upper face 16 of the automatic clamp is provided with slots 17 and 18 through which pass nails which are driven into the end of the side support for the purpose of preventing member 0 dlsplacement of the clamping device 9. The

surface 19 which engages the friction surface of the central support member 4: is slightly curved and is provided with a series or" serrations or corrugations 19 extending across the clamp from one end to the opposite end. These corrugations are pressed against the surface of the central located beneath the end support member a when the clampingde,

vice is secured in its memberv locking position. The automatic clamp 15 has its ournai mounting apertures 20' located 111 such a position relatively to the curved surface 19 as to bring its journal nearer the apex 21 formed by the surfaces 16 and 19, than to the opposite end 24 of the curved surface 19. This results in the clamp occupying a tilted position as shown in Figs. 1 and 2 when the clamp 13 is caus d to exert a pull upon the plates 10 in the direction of their axes for the reason that the journal pin exerts a greaterpressure at the edge 21 of the'curved surface 19 than at its opposite edge 24, because of the difference in the lengths of lever arms between the journal pin and the edge 21 and between the journal pin and the opposite edge 24 of the curved surface. This results in the clamp assuming a position in which a line of force will extend at right angles to the surface of the central support member 4, which surface forms a tangent to the curve of the surface 19 of the clamp when it occupies this position. The result of this is that the corrugations 19 will be pressed against the surface of the support member 4 with the upper end 22 of the automatic clamp in engagement with the lower end of the side support member 6.

The clamping device is secured in position by means of the clamp 13 when it is driven into engagement with the plate 14 located on the side support member 5, by hammering upon the surface 23 of the clamp. Vith the clamping device adjusted as above described to hold the support members of the strut in their adjusted positions, there can be no giving or settling of the membersrelatively to one another when the load is placed upon the strut, for the reason that downward movement of the members 5 and 6 with relation to the central support member will cause the cam shaped surface 19 to press with increasing pressure against the surface of the central support member 4 because of the eccentric location of thejournal pin with relation to adjacent points on the surface 19. Furthermore anytendency toward downward motion of the side support member 5 will tend to draw the clamp 13 into closer relation with the plate 14 and thus draw the sides of the side support mem bers 5 and 6 into increasing frictional engagement with the sides of the central support member 4, as well as also drawing the automatic clamp into engagement with the surface of the central support member 4 with its upper end 22 in lifting engagement with the side support member 6.

Having thus described my invention, what I claim is:

1. In combination in a strut a central support member, sidesupport members located on opposite sides of the central support member, and a clamping device adapted to ing device consisting of a clamp adapted to be driven into engagement with the outer face of one of sald side support members,

second clamp having an eccentric surface for engaging the opposite side of the central support member and a supporting surface for engaging the end of the other side support member, and means connecting the clamps, embracing the member, and adapted to cause said first mentioned clamp to bring the support surface of the said second mentioned clamp into engagement with the end of the other side support member when the first mentioned clamp is driven into clamping engagement with the first mentioned side support member.

2. A strut comprising central and side support members, and a clamping device adapted to secure the central and side support members in adjusted positions relatively to one another, said clamping device consisting of a clamp engaging one side of one of said side support members, a second clamp having a curved surface adapted to engage said central support member and a flat surface adapted tosupport one of said side support members, and means connecting the clamps and embracing the members for operating the second mentioned clamp when the first mentioned clamp is operated, whereby the second mentioned clamp will be rok'ed upon its curved surface to bring its fiat surface into supporting engagement with the side support member.

3. In an adjustable strut the combination of central and side support members, and a clamping device adapted to frictionally lock the members together, said clamping device comprising a. clamp, a second clamp, and means connecting the clamps, and embracing the members, said second clamp having a curved surface adapted to engage the central support member and a flat surface adapted to engage the side support member, said surfaces joining to form an apex, and a pivot located adjacent to the apex for connccting the clamp with said means, the

having a curved sur ace, and a flat surface joining the curved surface at an angle therehere jest, and. 

